Winches used in commercial applications are generally constructed and operated in a similar manner. The basic elements comprise a large-diameter steel spool or drum, brakes, a power source and assorted auxiliary devices. The primary function of the winch is to reel out and reel in the cable, in a controlled fashion by rotating the drum. The reeling out of the cable is largely powered by gravity. The reeling in of the cable is powered by the power source that is usually an electric motor or diesel engine, which is coupled to an intermediary gearing or drive system.
An example of a winch used in a commercial application is a drawworks used in oilfield drilling. The drawworks is a winch found on an oil rig on or below the rig deck. The primary function of the drawworks is to wind in and unwind the drilling line, a large diameter wire rope, as required. The drilling line is reeled over a crown block and traveling block to gain mechanical advantage in a “block and tackle” or “pulley” fashion. This reeling out and in of the drilling line causes the traveling block, and whatever may be hanging underneath it, to be lowered into or raised out of the well bore.
Conventional commercial winches, such as a drawworks winch, have the power source configured in an indirect drive manner with the power source positioned adjacent to the drum. The power source is connected to one or more gearboxes in a variety of ways including the use of drive shafts, couplings, transmissions or clutches. The gearbox in turn is connected to the drum using chain drives or other conventional drive mechanisms. Such indirect drive conventional drawworks systems have a number of disadvantages. First, an external power source occupies more space. In the context of the drawworks winch, the extra space required for the power source makes it difficult to place the drawworks in an optimal position on the already crowded oil rig. External power sources are noisy and can present a hazard to those working around them. Further, conventional winch systems, in particular the gearbox of conventional systems, require frequent maintenance and must be lubricated regularly. Many conventional winches employ complex lubrication systems for the drum and gearbox that require heating systems for the winter and cooling systems for the summer. Also, during the transmission of power through the indirect drive system, there are significant energy losses and a resulting inefficiency associated therewith.
Prior art suggestions at improved winches have been largely focused on providing sophisticated gearing mechanisms to use with the remote power source, and on improved braking systems to try and increase the safety of the winch systems. However, such suggestions do not address the previously described disadvantages and limitations of conventional winch systems.